1. Field of Invention
This invention relates to outdoor lighting fixtures, specifically to lighting fixture shields that are used for covering the light bulb in streetlights.
2. Description of Prior Art
In the design of roadways and parking lots, safety is always a major concern. One factor in the design of a safe road or parking lot is lighting, so that the driver or pedestrian is able to clearly see his surroundings at night. That is why streetlights were placed on roads and in parking lots. Most streetlights, however, use light inefficiently by dispersing light to where it is not needed. Such improper shielding leads to decreased visibility, and the inefficient use of light is a direct cause of light pollution. It is estimated that up to 50% of light pollution is caused by poor roadway lighting, and that inefficient lighting costs approximately $2 billion of energy per year in the United States alone.
One attempt by inventors and lighting companies to solve the problem of inefficient lighting was to use larger quantities of light to illuminate an area. This, however, is actually less efficient because large quantities of light can cause glare.
Several attempts have been made by other inventors and by commercial lighting companies to create luminaires that use light more efficiently by diffusing or reflecting light. Such lighting apparatuses as shown in U.S. Pat. No. 5,483,424 produce diffused light, but these are used mainly on film and television sets. Additionally, the light-reflecting elements are used to reflect light from an external source, such as the sun, and not from the bulb itself. The lighting fixtures described in U.S. Pat. Nos. 4,156,270 and 4,358,816 are used for very specific purposes, such as lighting billboards. These luminaires could not be used to light parking lots or other large areas.
The roadway luminaire described in U.S. Pat. No. 4,651,260 focuses on reflecting light to high angles of emissions, but does nothing to decrease light pollution or soften light to low angles of emissions. U.S. Pat. Nos. 4,270,161 and 4,337,507 provide lighting fixtures that decrease the amount of light thrown up into the atmosphere, but again do not decrease glare at small angles.
Several low level fixtures, such as those described in U.S. Pat. Nos. 3,593,014; 3,805,055, 3,833,804, and 5,055,987, attempt to decrease glare or utilize reflecting and diffusing techniques. However, these assemblies are mounted too low to the ground to illuminate a large area, sue as a roadway or parking lot. These light fixtures are designed to illuminate such small areas as driveways and garden pathways.
In view of the present disadvantages of currently available roadway lighting devices, it is desirable to redesign the luminaire to provide a light dispersion pattern that softens light at low angles, reflects light at high angles, and decreases light pollution. This will make the apparatus more efficient and therefore more cost-effective than the streetlights currently being used on roads and in parking lots.
In accordance with the present invention a streetlight shield comprises a standard lighting base, a translucent diffusing cylinder, a reflective strip wrapped around the cylinder, a highly-reflective truncated cone, and a minimally-reflective inverted cone.
Accordingly, several objects and advantages of this invention are:
(a) to provide a lighting shield which will diffuse light to small linear distances;
(b) to provide a lighting shield which will project light to large linear distances;
(c) to provide a lighting shield which will decrease light pollution over conventional streetlight designs;
(d) to provide a lighting shield which will increase the efficiency of the streetlight over currently-used designs by reducing the amount of light needed to illuminate an area, thereby decreasing energy costs;
(e) to provide a lighting shield that, when compared to currently-used streetlight designs, will improve visibility in outdoor areas lit with streetlightsxe2x80x94in other words, to provide a safer environment for drivers and pedestrians.
Further objects and advantages of this invention will become apparent from a consideration of the drawings and ensuing description.